Gene expression profiling on mouse models of cardiomyopathies

Adjuvant chemotherapy of anthracycline derivatives with antibodies against erbB2 (i.e. trastuzumab, herceptin) is highly effective for a subset of mammary tumors overexpressing erbB2 oncogen. However, an undesired effect of the combined treatment is the increase incidence of dilated cardiomyopathies that may affect a 30% subpopulation of these patients. The accumulating evidence demonstrates the essential role of neuregulin signaling in the adult heart, and morerover, indicates that an impaired neuregulin signaling exacerbates the doxorubicin-mediated cardiac toxicity. Despite this strong evidence, the precise molecular interactions and the specific cardiomyocyte targets of the active erbB2/erbB4 heterodimer remain unknown. In this study, we examined potential molecular targets and mechanisms underlying the synergistic cardiotoxicity of anthracyclines in the ventricular muscle specific erbB4 knockout mouse. We employed a DNA microarray to assess the characteristic gene expression profile, whose partial data was verified by real time RT-PCR and then, grouped in functional categories and pathways. From this study, we demonstrate the upregulation of genes related to the classical signature of a hypertrophic response, shared by the 3 models. In addition, these results revealed an erbB-dependent hypertrophic response through the interaction with G-protein coupled receptors, a commonality in the 3 models. A robust upregulation of EGF and HB-EGF and pleitrophin implicated in cardiac growth together with the remarkable downregulation of IGF-I/PI 3`Kinase pathway characterize the doxorubicin-treated erbB4-KO mice. This defect together with metabolic abnormalities appears to be underlying the phenotypic modification of cardiomyocytes in doxorubicin-treated erbB4-KO mouse. For each mouse model investigated RNA of 4-8 individuals was pooled and targets were hybridised in four technical replicates on agilent cDNA microarrays. In a two color approach two dye swaps were performed with the cardiomyopathy samples and their wildtype/healty controls.